diff --git a/libs/binder/RpcServer.cpp b/libs/binder/RpcServer.cpp
index ad9ba96..ad04702 100644
--- a/libs/binder/RpcServer.cpp
+++ b/libs/binder/RpcServer.cpp
@@ -23,6 +23,8 @@
 #include <thread>
 #include <vector>
 
+#include <android-base/file.h>
+#include <android-base/hex.h>
 #include <android-base/scopeguard.h>
 #include <binder/Parcel.h>
 #include <binder/RpcServer.h>
@@ -290,17 +292,29 @@
         }
     }
 
+    std::vector<uint8_t> sessionId;
+    if (status == OK) {
+        if (header.sessionIdSize > 0) {
+            sessionId.resize(header.sessionIdSize);
+            status = client->interruptableReadFully(server->mShutdownTrigger.get(),
+                                                    sessionId.data(), sessionId.size());
+            if (status != OK) {
+                ALOGE("Failed to read session ID for client connecting to RPC server: %s",
+                      statusToString(status).c_str());
+                // still need to cleanup before we can return
+            }
+        }
+    }
+
     bool incoming = false;
     uint32_t protocolVersion = 0;
-    RpcAddress sessionId = RpcAddress::zero();
     bool requestingNewSession = false;
 
     if (status == OK) {
         incoming = header.options & RPC_CONNECTION_OPTION_INCOMING;
         protocolVersion = std::min(header.version,
                                    server->mProtocolVersion.value_or(RPC_WIRE_PROTOCOL_VERSION));
-        sessionId = RpcAddress::fromRawEmbedded(&header.sessionId);
-        requestingNewSession = sessionId.isZero();
+        requestingNewSession = sessionId.empty();
 
         if (requestingNewSession) {
             RpcNewSessionResponse response{
@@ -342,15 +356,26 @@
                 return;
             }
 
+            // Uniquely identify session at the application layer. Even if a
+            // client/server use the same certificates, if they create multiple
+            // sessions, we still want to distinguish between them.
+            constexpr size_t kSessionIdSize = 32;
+            sessionId.resize(kSessionIdSize);
             size_t tries = 0;
             do {
                 // don't block if there is some entropy issue
                 if (tries++ > 5) {
-                    ALOGE("Cannot find new address: %s", sessionId.toString().c_str());
+                    ALOGE("Cannot find new address: %s",
+                          base::HexString(sessionId.data(), sessionId.size()).c_str());
                     return;
                 }
 
-                sessionId = RpcAddress::random(true /*forServer*/);
+                base::unique_fd fd(TEMP_FAILURE_RETRY(
+                        open("/dev/urandom", O_RDONLY | O_CLOEXEC | O_NOFOLLOW)));
+                if (!base::ReadFully(fd, sessionId.data(), sessionId.size())) {
+                    ALOGE("Could not read from /dev/urandom to create session ID");
+                    return;
+                }
             } while (server->mSessions.end() != server->mSessions.find(sessionId));
 
             session = RpcSession::make();
@@ -370,7 +395,7 @@
             auto it = server->mSessions.find(sessionId);
             if (it == server->mSessions.end()) {
                 ALOGE("Cannot add thread, no record of session with ID %s",
-                      sessionId.toString().c_str());
+                      base::HexString(sessionId.data(), sessionId.size()).c_str());
                 return;
             }
             session = it->second;
@@ -432,16 +457,17 @@
 }
 
 void RpcServer::onSessionAllIncomingThreadsEnded(const sp<RpcSession>& session) {
-    auto id = session->mId;
-    LOG_ALWAYS_FATAL_IF(id == std::nullopt, "Server sessions must be initialized with ID");
-    LOG_RPC_DETAIL("Dropping session with address %s", id->toString().c_str());
+    const std::vector<uint8_t>& id = session->mId;
+    LOG_ALWAYS_FATAL_IF(id.empty(), "Server sessions must be initialized with ID");
+    LOG_RPC_DETAIL("Dropping session with address %s",
+                   base::HexString(id.data(), id.size()).c_str());
 
     std::lock_guard<std::mutex> _l(mLock);
-    auto it = mSessions.find(*id);
+    auto it = mSessions.find(id);
     LOG_ALWAYS_FATAL_IF(it == mSessions.end(), "Bad state, unknown session id %s",
-                        id->toString().c_str());
+                        base::HexString(id.data(), id.size()).c_str());
     LOG_ALWAYS_FATAL_IF(it->second != session, "Bad state, session has id mismatch %s",
-                        id->toString().c_str());
+                        base::HexString(id.data(), id.size()).c_str());
     (void)mSessions.erase(it);
 }
 
diff --git a/libs/binder/RpcSession.cpp b/libs/binder/RpcSession.cpp
index c57b749..a99e061 100644
--- a/libs/binder/RpcSession.cpp
+++ b/libs/binder/RpcSession.cpp
@@ -26,6 +26,7 @@
 
 #include <string_view>
 
+#include <android-base/hex.h>
 #include <android-base/macros.h>
 #include <android_runtime/vm.h>
 #include <binder/Parcel.h>
@@ -143,7 +144,7 @@
 }
 
 status_t RpcSession::setupPreconnectedClient(unique_fd fd, std::function<unique_fd()>&& request) {
-    return setupClient([&](const RpcAddress& sessionId, bool incoming) -> status_t {
+    return setupClient([&](const std::vector<uint8_t>& sessionId, bool incoming) -> status_t {
         // std::move'd from fd becomes -1 (!ok())
         if (!fd.ok()) {
             fd = request();
@@ -244,12 +245,11 @@
                                                 ConnectionUse::CLIENT, &connection);
     if (status != OK) return status;
 
-    mId = RpcAddress::zero();
-    status = state()->getSessionId(connection.get(), sp<RpcSession>::fromExisting(this),
-                                   &mId.value());
+    status = state()->getSessionId(connection.get(), sp<RpcSession>::fromExisting(this), &mId);
     if (status != OK) return status;
 
-    LOG_RPC_DETAIL("RpcSession %p has id %s", this, mId->toString().c_str());
+    LOG_RPC_DETAIL("RpcSession %p has id %s", this,
+                   base::HexString(mId.data(), mId.size()).c_str());
     return OK;
 }
 
@@ -408,8 +408,8 @@
     return server;
 }
 
-status_t RpcSession::setupClient(
-        const std::function<status_t(const RpcAddress& sessionId, bool incoming)>& connectAndInit) {
+status_t RpcSession::setupClient(const std::function<status_t(const std::vector<uint8_t>& sessionId,
+                                                              bool incoming)>& connectAndInit) {
     {
         std::lock_guard<std::mutex> _l(mMutex);
         LOG_ALWAYS_FATAL_IF(mOutgoingConnections.size() != 0,
@@ -418,8 +418,7 @@
     }
     if (auto status = initShutdownTrigger(); status != OK) return status;
 
-    if (status_t status = connectAndInit(RpcAddress::zero(), false /*incoming*/); status != OK)
-        return status;
+    if (status_t status = connectAndInit({}, false /*incoming*/); status != OK) return status;
 
     {
         ExclusiveConnection connection;
@@ -460,26 +459,25 @@
 
     // we've already setup one client
     for (size_t i = 0; i + 1 < numThreadsAvailable; i++) {
-        if (status_t status = connectAndInit(mId.value(), false /*incoming*/); status != OK)
-            return status;
+        if (status_t status = connectAndInit(mId, false /*incoming*/); status != OK) return status;
     }
 
     for (size_t i = 0; i < mMaxThreads; i++) {
-        if (status_t status = connectAndInit(mId.value(), true /*incoming*/); status != OK)
-            return status;
+        if (status_t status = connectAndInit(mId, true /*incoming*/); status != OK) return status;
     }
 
     return OK;
 }
 
 status_t RpcSession::setupSocketClient(const RpcSocketAddress& addr) {
-    return setupClient([&](const RpcAddress& sessionId, bool incoming) {
+    return setupClient([&](const std::vector<uint8_t>& sessionId, bool incoming) {
         return setupOneSocketConnection(addr, sessionId, incoming);
     });
 }
 
 status_t RpcSession::setupOneSocketConnection(const RpcSocketAddress& addr,
-                                              const RpcAddress& sessionId, bool incoming) {
+                                              const std::vector<uint8_t>& sessionId,
+                                              bool incoming) {
     for (size_t tries = 0; tries < 5; tries++) {
         if (tries > 0) usleep(10000);
 
@@ -537,7 +535,7 @@
     return UNKNOWN_ERROR;
 }
 
-status_t RpcSession::initAndAddConnection(unique_fd fd, const RpcAddress& sessionId,
+status_t RpcSession::initAndAddConnection(unique_fd fd, const std::vector<uint8_t>& sessionId,
                                           bool incoming) {
     LOG_ALWAYS_FATAL_IF(mShutdownTrigger == nullptr);
     auto server = mCtx->newTransport(std::move(fd), mShutdownTrigger.get());
@@ -548,13 +546,20 @@
 
     LOG_RPC_DETAIL("Socket at client with RpcTransport %p", server.get());
 
+    if (sessionId.size() > std::numeric_limits<uint16_t>::max()) {
+        ALOGE("Session ID too big %zu", sessionId.size());
+        return BAD_VALUE;
+    }
+
     RpcConnectionHeader header{
             .version = mProtocolVersion.value_or(RPC_WIRE_PROTOCOL_VERSION),
             .options = 0,
+            .sessionIdSize = static_cast<uint16_t>(sessionId.size()),
     };
-    memcpy(&header.sessionId, &sessionId.viewRawEmbedded(), sizeof(RpcWireAddress));
 
-    if (incoming) header.options |= RPC_CONNECTION_OPTION_INCOMING;
+    if (incoming) {
+        header.options |= RPC_CONNECTION_OPTION_INCOMING;
+    }
 
     auto sendHeaderStatus =
             server->interruptableWriteFully(mShutdownTrigger.get(), &header, sizeof(header));
@@ -564,6 +569,18 @@
         return sendHeaderStatus;
     }
 
+    if (sessionId.size() > 0) {
+        auto sendSessionIdStatus =
+                server->interruptableWriteFully(mShutdownTrigger.get(), sessionId.data(),
+                                                sessionId.size());
+        if (sendSessionIdStatus != OK) {
+            ALOGE("Could not write session ID ('%s') to socket: %s",
+                  base::HexString(sessionId.data(), sessionId.size()).c_str(),
+                  statusToString(sendSessionIdStatus).c_str());
+            return sendSessionIdStatus;
+        }
+    }
+
     LOG_RPC_DETAIL("Socket at client: header sent");
 
     if (incoming) {
@@ -636,7 +653,7 @@
 }
 
 bool RpcSession::setForServer(const wp<RpcServer>& server, const wp<EventListener>& eventListener,
-                              const RpcAddress& sessionId) {
+                              const std::vector<uint8_t>& sessionId) {
     LOG_ALWAYS_FATAL_IF(mForServer != nullptr);
     LOG_ALWAYS_FATAL_IF(server == nullptr);
     LOG_ALWAYS_FATAL_IF(mEventListener != nullptr);
diff --git a/libs/binder/RpcState.cpp b/libs/binder/RpcState.cpp
index b58f1b3..f181a7b 100644
--- a/libs/binder/RpcState.cpp
+++ b/libs/binder/RpcState.cpp
@@ -397,7 +397,7 @@
 }
 
 status_t RpcState::getSessionId(const sp<RpcSession::RpcConnection>& connection,
-                                const sp<RpcSession>& session, RpcAddress* sessionIdOut) {
+                                const sp<RpcSession>& session, std::vector<uint8_t>* sessionIdOut) {
     Parcel data;
     data.markForRpc(session);
     Parcel reply;
@@ -410,7 +410,7 @@
         return status;
     }
 
-    return sessionIdOut->readFromParcel(reply);
+    return reply.readByteVector(sessionIdOut);
 }
 
 status_t RpcState::transact(const sp<RpcSession::RpcConnection>& connection,
@@ -792,7 +792,7 @@
                     // for client connections, this should always report the value
                     // originally returned from the server, so this is asserting
                     // that it exists
-                    replyStatus = session->mId.value().writeToParcel(&reply);
+                    replyStatus = reply.writeByteVector(session->mId);
                     break;
                 }
                 default: {
diff --git a/libs/binder/RpcState.h b/libs/binder/RpcState.h
index 1446eec..b8cf2db 100644
--- a/libs/binder/RpcState.h
+++ b/libs/binder/RpcState.h
@@ -73,7 +73,7 @@
     status_t getMaxThreads(const sp<RpcSession::RpcConnection>& connection,
                            const sp<RpcSession>& session, size_t* maxThreadsOut);
     status_t getSessionId(const sp<RpcSession::RpcConnection>& connection,
-                          const sp<RpcSession>& session, RpcAddress* sessionIdOut);
+                          const sp<RpcSession>& session, std::vector<uint8_t>* sessionIdOut);
 
     [[nodiscard]] status_t transact(const sp<RpcSession::RpcConnection>& connection,
                                     const sp<IBinder>& address, uint32_t code, const Parcel& data,
diff --git a/libs/binder/RpcWireFormat.h b/libs/binder/RpcWireFormat.h
index 067c4ad..fbcfac6 100644
--- a/libs/binder/RpcWireFormat.h
+++ b/libs/binder/RpcWireFormat.h
@@ -20,9 +20,7 @@
 #pragma clang diagnostic push
 #pragma clang diagnostic error "-Wpadded"
 
-enum : uint8_t {
-    RPC_CONNECTION_OPTION_INCOMING = 0x1, // default is outgoing
-};
+constexpr uint8_t RPC_CONNECTION_OPTION_INCOMING = 0x1; // default is outgoing
 
 constexpr uint64_t RPC_WIRE_ADDRESS_OPTION_CREATED = 1 << 0; // distinguish from '0' address
 constexpr uint64_t RPC_WIRE_ADDRESS_OPTION_FOR_SERVER = 1 << 1;
@@ -39,12 +37,13 @@
  */
 struct RpcConnectionHeader {
     uint32_t version; // maximum supported by caller
-    uint8_t reserver0[4];
-    RpcWireAddress sessionId;
     uint8_t options;
-    uint8_t reserved1[7];
+    uint8_t reservered[9];
+    // Follows is sessionIdSize bytes.
+    // if size is 0, this is requesting a new session.
+    uint16_t sessionIdSize;
 };
-static_assert(sizeof(RpcConnectionHeader) == 56);
+static_assert(sizeof(RpcConnectionHeader) == 16);
 
 /**
  * In response to an RpcConnectionHeader which corresponds to a new session,
diff --git a/libs/binder/include/binder/RpcServer.h b/libs/binder/include/binder/RpcServer.h
index d0e4e27..b698890 100644
--- a/libs/binder/include/binder/RpcServer.h
+++ b/libs/binder/include/binder/RpcServer.h
@@ -17,7 +17,6 @@
 
 #include <android-base/unique_fd.h>
 #include <binder/IBinder.h>
-#include <binder/RpcAddress.h>
 #include <binder/RpcSession.h>
 #include <binder/RpcTransport.h>
 #include <utils/Errors.h>
@@ -201,7 +200,7 @@
     std::map<std::thread::id, std::thread> mConnectingThreads;
     sp<IBinder> mRootObject;
     wp<IBinder> mRootObjectWeak;
-    std::map<RpcAddress, sp<RpcSession>> mSessions;
+    std::map<std::vector<uint8_t>, sp<RpcSession>> mSessions;
     std::unique_ptr<FdTrigger> mShutdownTrigger;
     std::condition_variable mShutdownCv;
 };
diff --git a/libs/binder/include/binder/RpcSession.h b/libs/binder/include/binder/RpcSession.h
index d92af0a..7dfbd23 100644
--- a/libs/binder/include/binder/RpcSession.h
+++ b/libs/binder/include/binder/RpcSession.h
@@ -222,19 +222,21 @@
     static void join(sp<RpcSession>&& session, PreJoinSetupResult&& result);
 
     [[nodiscard]] status_t setupClient(
-            const std::function<status_t(const RpcAddress& sessionId, bool incoming)>&
+            const std::function<status_t(const std::vector<uint8_t>& sessionId, bool incoming)>&
                     connectAndInit);
     [[nodiscard]] status_t setupSocketClient(const RpcSocketAddress& address);
     [[nodiscard]] status_t setupOneSocketConnection(const RpcSocketAddress& address,
-                                                    const RpcAddress& sessionId, bool incoming);
-    [[nodiscard]] status_t initAndAddConnection(base::unique_fd fd, const RpcAddress& sessionId,
+                                                    const std::vector<uint8_t>& sessionId,
+                                                    bool incoming);
+    [[nodiscard]] status_t initAndAddConnection(base::unique_fd fd,
+                                                const std::vector<uint8_t>& sessionId,
                                                 bool incoming);
     [[nodiscard]] status_t addIncomingConnection(std::unique_ptr<RpcTransport> rpcTransport);
     [[nodiscard]] status_t addOutgoingConnection(std::unique_ptr<RpcTransport> rpcTransport,
                                                  bool init);
     [[nodiscard]] bool setForServer(const wp<RpcServer>& server,
                                     const wp<RpcSession::EventListener>& eventListener,
-                                    const RpcAddress& sessionId);
+                                    const std::vector<uint8_t>& sessionId);
     sp<RpcConnection> assignIncomingConnectionToThisThread(
             std::unique_ptr<RpcTransport> rpcTransport);
     [[nodiscard]] bool removeIncomingConnection(const sp<RpcConnection>& connection);
@@ -291,7 +293,7 @@
     sp<WaitForShutdownListener> mShutdownListener; // used for client sessions
     wp<EventListener> mEventListener; // mForServer if server, mShutdownListener if client
 
-    std::optional<RpcAddress> mId;
+    std::vector<uint8_t> mId;
 
     std::unique_ptr<FdTrigger> mShutdownTrigger;